The 4th annual Hammer Open Air Metal Festival will be held between 19 and 20 July 2013 in Mannin Navetta, Lieto (Finland). A total of 24 bands will be playing during two days, drinks will be yet again reasonable priced (in Finnish proportion, that is) and the atmosphere is something you will not experience in other festivals in Finland.
Don't want to stay inside the festival area for the whole day? You can leave and re-enter the festival area at any time during it's opening hours.
Cloak room cost is 3 EUR (visiting the cloak room is free of charge).

How often does the shuttle bus run? Does it go from the market place or the bus station? I'm currently trying to figure out the best way to get from Helsinki airport to Turku, but I need to try and co-ordinate where I should aim to get to.